Question

In which direction does DNA replication take place?

a. 5'-3'

b. 3'-5'

c. 5'

d. 3'

Short answer

Option a is the correct answer.

Step-by-step solution

Introduction

Deoxyribonucleotides, the DNA's building blocks, are converted into DNA molecules with the assistance of the DNA polymerase enzyme. They normally work in pairs to produce identical DNA strands and are crucial for DNA replication.

The explanation for the correct answer.

Nucleotides are only added to the 3' end of the developing strand since DNA is always produced in the 5'-to-3' orientation. The 3'-OH group of the last nucleotide of the developing strand is bound by the 5'-phosphate group of the next nucleotide.

The 3' OH group is necessary for DNA polymerases to begin the synthesis of a DNA strand. As a result, by expanding the 3' end of the current nucleotide chain, it can only synthesize in one direction i.e., in the 5'-to-3' orientation. Therefore, the rest of the options are irrelevant.

Explanation of incorrect options

DNA replication takes place in 5'-3' direction, so other options are incorrect.